Di-substituted cyanamides are useful intermediates for the synthesis of symmetrical secondary amines. Unfortunately, this method of obtaining secondary amines is handicapped by the lack of a practical method for preparing di-substituted cyanamides.
In a procedure reported by E. B. Vliet, Organic Synthesis, Collective Vol. I, 203-4 (1932), calcium cyanamide is reacted with caustic to form disodium cyanamide, which is subsequently reacted with allyl bromide to form diallyl cyanamide. This procedure requires considerable manipulations and many processing steps, producing a product of low yield.
Improvements have been suggested through the incorporation of a dipolar aprotic solvent. One such method is disclosed by A. Donetti et al., Tetrahedron Letters 39, 3327-8 (1969). This method requires anhydrous cyanamide and dimethyl sulfoxide ion as reagents. A dipolar aprotic solvent was also used by Rider, U.S. Pat. No. 3,692,832, Sept. 19, 1972, in conjunction with alkali metal carbonates or bicarbonates.